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| United States Patent |
6,143,041
|
|
Nozawa
, et al.
|
November 7, 2000
|
Process for manufacturing a button type alkaline battery
Abstract
A method for manufacturing a button-type alkaline cell comprises forming
and working a negative electrode having an inner surface of Cu using a die
having a ceramic portion while abutting the ceramic portion of the die
with at least the Cu inner surface of the negative electrode. The thus
formed and worked negative electrode is then combined with a positive
electrode compound, a negative electrode compound, a separator, a positive
electrode, a gasket and an alkaline electrolyte to form the button-type
alkaline cell.
| Inventors:
|
Nozawa; Mutsuo (Sendai, JP);
Tanno; Koji (Sendai, JP);
Takahashi; Kazuyuki (Sendai, JP);
Ishizaki; Morio (Itami, JP)
|
| Assignee:
|
SII Micro Parts Ltd. (JP);
Ishizaki Press Ind. Co. Ltd. (JP)
|
| Appl. No.:
|
860128 |
| Filed:
|
September 12, 1997 |
| PCT Filed:
|
November 1, 1996
|
| PCT NO:
|
PCT/JP96/03214
|
| 371 Date:
|
September 12, 1997
|
| 102(e) Date:
|
September 12, 1997
|
| PCT PUB.NO.:
|
WO97/16858 |
| PCT PUB. Date:
|
May 9, 1997 |
Foreign Application Priority Data
| Jan 11, 1995[JP] | 7-285342 |
| Apr 12, 1996[JP] | 8-091468 |
| Oct 30, 1996[JP] | 8-287852 |
| Current U.S. Class: |
29/623.1; 429/206 |
| Intern'l Class: |
H01M 002/04 |
| Field of Search: |
29/623.1
429/206
|
References Cited
U.S. Patent Documents
| 4442186 | Apr., 1984 | Urry.
| |
| 4861688 | Aug., 1989 | Miura et al. | 429/206.
|
| 4882238 | Nov., 1989 | Yoshioka et al.
| |
| Foreign Patent Documents |
| 3602485 | Jan., 1986 | DE.
| |
| 3602485A1 | Jul., 1986 | DE.
| |
Primary Examiner: Maples; John S.
Attorney, Agent or Firm: Adams & Wilks
Claims
We claim:
1. A method for manufacturing a button-type alkaline cell, comprising the
steps of:
forming and working a negative electrode can having an inner surface of Cu
using a die having a ceramic portion while abutting the ceramic portion of
the die with at least the Cu inner surface of the negative electrode can;
and
combining the negative electrode can with a positive electrode compound, a
negative electrode compound, a separator, a positive electrode can, a
gasket and an alkaline electrolyte to form the button-type alkaline cell.
2. A method for manufacturing a button-type alkaline cell according to
claim 1; wherein the die has a reinforcing portion at a side opposite to
the ceramic portion for reinforcing the ceramic portion to which a load is
applied during the steps of forming and working the negative electrode
can.
3. A method for manufacturing a button-type cell according to claim 2;
wherein the reinforcing portion comprises cemented carbide or tool steel.
4. A method for manufacturing a button-type cell according to claim 2;
wherein the ceramic portion comprises a material selected from the group
consisting of zirconium oxide, silicon boride and silicon nitride.
5. A method for manufacturing a button-type cell according to claim 2;
wherein the step of forming and working the negative electrode can
comprises forming and working a main body composed of a laminated metallic
material, disposing Ni on a first surface of the main body, and disposing
Cu on a second surface of the main body opposite the first surface.
6. A method for manufacturing a button-type alkaline cell according to
claim 1; wherein the die has a reinforcing portion, and wherein the
ceramic portion comprises a ceramic material coated on a surface of the
reinforcing portion.
7. A method for manufacturing a button-type cell according to claim 6;
wherein the ceramic portion comprises a material selected from the group
consisting of zirconium oxide, silicon boride and silicon nitride.
8. A method for manufacturing a button-type cell according to claim 6;
wherein the step of forming and working the negative electrode can
comprises forming and working a main body composed of a laminated metallic
material, disposing Ni on a first surface of the main body, and disposing
Cu on a second surface of the main body opposite the first surface.
9. A method for manufacturing a button-type alkaline cell according to
claim 6; wherein the reinforcing portion comprises cemented carbide or
tool steel.
10. A method for manufacturing a button-type cell according to claim 9;
wherein the step of forming and working the negative electrode can
comprises forming and working a main body composed of a laminated metallic
material, disposing Ni on a first surface of the main body, and disposing
Cu on a second surface of the main body opposite the first surface.
11. A method for manufacturing a button-type alkaline cell according to
claim 9; wherein the ceramic portion comprises a material selected from
the group consisting of zirconium oxide, silicon boride and silicon
nitride.
12. A method for manufacturing a button-type alkaline cell according to
claim 11; wherein the step of forming and working the negative electrode
can comprises forming and working a main body composed of a laminated
metallic material, disposing Ni on a first surface of the main body, and
disposing Cu on a second surface of the main body opposite the first
surface.
13. A method for manufacturing a button-type alkaline cell according to
claim 12; wherein the laminated metallic material comprises a clad of
Ni--SUS--Cu.
14. A method for manufacturing a button-type alkaline cell according to
claim 12; wherein the laminated metallic material comprises Ni plated on a
clad of SUS--Cu or a clad of Cu and deep drawing steel.
15. A method for manufacturing a button-type alkaline cell according to
claim 14; wherein the negative electrode compound does not contain
mercury.
16. A method for manufacturing a button-type cell according to claim 12;
wherein the laminated metallic material comprises steel.
17. A method for manufacturing a button-type cell according to claim 1;
wherein the ceramic portion comprises a material selected from the group
consisting of zirconium oxide, silicon boride and silicon nitride.
18. A method for manufacturing a button-type cell according to claim 1;
wherein the step of forming and working the negative electrode can
comprises forming and working a main body composed of a laminated metallic
material, disposing Ni on a first surface of the main body, and disposing
Cu on a second surface of the main body opposite the first surface.
19. A method for manufacturing a button-type alkaline cell according to
claim 1; wherein the negative electrode compound does not contain mercury.
Description
TECHNICAL FIELD
The present invention relates to an improvement of a manufacturing method
of a button type alkaline cell. It is to provide a button type alkaline
cell, having a good self-discharge characteristic, manufactured by
combining a negative electrode can made from a raw material of steel on
which Ni is provided at one surface thereof and Cu is provided at the
other surface thereof and which is fabricated by using a die whose part
abutting at least with the Cu surface is ceramics, with other components
of the cell such as a positive electrode compound, a negative electrode
compound, a separator, a positive electrode can, a gasket and an alkaline
electrolyte. It is to provide, specifically, a button type alkaline cell
containing a very little amount of mercury or no mercury at all and a
manufacturing method thereof.
BACKGROUND ART
Hitherto, a button type alkaline cell is manufactured by fabricating a
negative electrode can by using metallic molds such as a die, a punch and
a blank holder made from tool steel, high speed steel or cemented carbide
and by combining it with other components such as a positive electrode
compound, a negative electrode compound, a separator, a positive electrode
can, a gasket and a alkaline electrolyte.
As raw materials of the negative electrode can of the button type alkaline
cell, an Ni--SUS--Cu clad material or a material in which Ni is plated on
the side opposite from Cu which becomes the inner surface of the negative
electrode can on a laminated material of Cu and SUS or Cu and a deep
drawing steel is used. The negative electrode can is fabricated by working
the raw material using a die made from tool steel or cemented carbide. The
button type alkaline cell is manufactured by combining this negative
electrode can with the other components such as the negative electrode
compound mainly composed of zinc, the positive electrode compound mainly
composed of silver oxide, the separator, the electrolyte, the positive
electrode can and the gasket.
However, the button type alkaline cell using the negative electrode can
manufactured by using the prior art die, in which tool steel or cemented
carbide is used for the part which contacts with the Cu surface, generates
gas from the Cu surface when the negative electrode zinc contacts with the
alkaline electrolyte and when part of the electrolyte decomposes. It is
because Fe of the tool steel, Co or Ni used as a binder of the cemented
carbide or W which is the base material of the cemented carbide is
transferred and adheres on the Cu surface, i.e. the inner surface of the
negative electrode can, during working of the negative electrode can,
though it is a very small amount. The generation of gas leads to the
exhaustion of the negative electrode compound within the button type
alkaline cell, thus deteriorating the self-discharge characteristic of the
cell.
Although the gas may be suppressed from generating by containing mercury
within the negative electrode compound because the degree of generation of
gas may be reduced as the mercury covers the Cu surface, there is
apprehension that the environment might be contaminated by the mercury
contained within the disposed cells.
Although it has been attempted to reduce the amount of mercury by fully
cleaning the negative electrode can or by adding indium and bismuth in
order to reduce the amount of mercury contained within the button type
alkaline cell and to maintain the effect of suppressing the generation of
gas (e.g. Japanese Patent Laid-Open Nos. Hei. 8-31428, Hei. 8-130021 and
others), it is difficult to prevent the gas from generating from the inner
surface of the negative electrode can.
SUMMARY OF THE INVENTION
Then, according to the present invention, a negative electrode can having
an inner surface of Cu is formed and worked by a die whose part abutting
at least with the Cu surface is ceramic. More preferably, the negative
electrode can is worked by using a die coated with ceramic. While there is
a number of types of ceramics which can be used as the coating for the
die, zirconium oxide, silicon boride, or silicon nitride having a good
impact resistance is desirable in particular.
According to the present invention, in manufacturing a button type alkaline
cell having a negative electrode compound of zinc containing a small
amount of mercury or no mercury at all, the negative electrode can having
the inner surface of Cu is formed and worked by a die whose part abutting
at least with the Cu surface is ceramic. It is preferable to provide a
reinforcing portion because ceramic is normally weak to a bending load.
The reinforcement is made by providing a raw material such as tool steel
and cemented carbide on the surface opposite from the surface of the
ceramic to which the load is applied. It is possible to realize a
structure in which the ceramic is provided at the part of the die
contacting with the Cu surface of the negative electrode can and the
reinforcing portion is provided on the opposite side from the portion of
the ceramic to which the load is applied by using a die in which ceramic
is coated on the surface of cemented carbide or steel.
No Fe is transferred from the steel and no Co, Ni or W is transferred from
the cemented carbide when the negative electrode can formed and worked by
such die is used. For the ceramics to be used, zirconium oxide, silicon
boride, and silicon nitride are excellent in terms of abrasion resistance,
impact resistance and chemical resistance.
Accordingly, an amount of gas generated when the negative electrode can of
the present invention contacts with the negative electrode compound and
alkaline electrolyte is reduced considerably as compared to the prior art
case. The effect of reducing the generation of gas is remarkable when
negative electrode zinc containing a little amount of mercury or no
mercury at all is used.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a flow diagram showing manufacturing steps of a button type
alkaline cell of the present invention;
FIGS. 2a through 2c are section views of a main part of one exemplary die
for manufacturing a negative electrode can of the button type alkaline
cell of the present invention;
FIG. 3 is a section view of the button type alkaline cell according to a
preferred embodiment of the present invention;
FIG. 4 is a section view showing an example of a punch portion and a
wrinkle pressing portion of a die for the negative electrode can made from
ceramics reinforced by tool steel; and
FIG. 5 is a partial section view showing an exemplary ceramic die
reinforced by cemented carbide.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the present invention will be explained below.
First Embodiment
FIG. 3 is a section view of a silver oxide cell SR512SW which is one
example of a button type alkaline cell of the present invention, and FIGS.
2a through 2c are section views showing the main part of a die used in
manufacturing a negative electrode can of the silver oxide cell SR512SW in
FIG. 3.
Parts of the die are manufactured first and a ceramic coating mainly
composed of zirconium oxide is applied to parts 7, 8 and 9 among the parts
of the die in FIGS. 2a through 2c which abut with a Cu surface of the
negative electrode can. They are then assembled and adjusted as the die.
The negative electrode can 5 is manufactured by using the die and by using
Ni--SUS--Cu as its raw material.
Next, a positive electrode compound 2 is poured into a positive electrode
can 1, a separator 3 is placed on the positive electrode can, a gasket 6
is inserted and an electrolyte composed of a negative electrode compound 4
and NaOH is injected to the gasket. Then, after covering it with the lid
of the negative electrode can 5, an opening of the negative electrode can
1 is caulked to seal it. FIG. 1 shows its process.
Two kinds of silver oxide cells SR512SW, one containing and the other not
containing mercury in the negative electrode zinc, were manufactured as
the inventive and prior art cells, respectively. Table 1 shows values of
the degree of self-discharge thereof measured from discharge capacity in
the early period from the production and from that after keeping them for
20 days in an environment of 60.degree. C. The measurements were
calculated from an average of six each.
TABLE 1
______________________________________
Containing Hg in
Containing No Hg in
Negative Electrode Can
Negative Electrode Can
______________________________________
Present Invention
0.8% 1.4%
Prior Art 3.1% 4.8%
______________________________________
Second Embodiment
Another embodiment of the present invention will be explained below.
A type of cell is silver oxide cell SR626SW whose sectional profile is the
same with that shown in FIG. 3. FIG. 4 is a section view of the main part
of a die used in manufacturing a negative electrode can of the present
embodiment. FIG. 5 is a section view of a die for bending a turn-up
portion at the periphery of the negative electrode can. It is constructed
such that a cemented carbide ring is embedded as a reinforcing portion
into a holding portion made from tool steel so as to hold the ceramic die
therein. The ceramics in FIGS. 4 and 5 are zirconium oxide. The negative
electrode can is manufactured by trimming a disc of required size from a
stripe of Ni--SUS--Cu clad, i.e. the raw material, by creating a cavity by
a punch shown in FIG. 4 and by bending the periphery by the die shown in
FIG. 5. After fabricating the negative electrode can 5, the positive
electrode compound 2 is poured into the positive electrode can 1, the
separator 3 is placed on the positive electrode can, the gasket 6 is
inserted and the electrolyte composed of negative electrode compound 4 and
NaOH is injected into the gasket. Then, after covering it by the lid of
the negative electrode can 5, the opening of the negative electrode can 1
is caulked to seal it.
Two kinds of cells, one containing and the other not containing mercury in
the negative electrode zinc were manufactured as the inventive and prior
art cells, respectively. Table 2 shows values of degree of self-discharge
thereof measured from discharge capacity in the early period from the
production and from that after keeping them for 40 days in an environment
of 60.degree. C. The measurements were calculated from an average of six
each.
TABLE 2
______________________________________
Containing Hg in
Containing No Hg in
Negative Electrode Can
Negative Electrode Can
______________________________________
Present Invention
1.8% 8.2%
Prior Art 6.5% 13.4%
______________________________________
It is apparent from these results that the present invention is effective
in improving the self-discharge characteristic of all the cells such as a
silver oxide cell, an alkali-manganese cell, an air-zinc cell and others
having the Cu surface inside and containing the negative electrode
compound mainly composed of zinc and the alkaline electrolyte. Further,
because these effects are brought about with respect to working of the Cu
surface, it is apparent that the present invention is effective also to
any raw material so long as it is a raw material in which Cu is laminated
with steel.
It is noted that although 5% to 10% of mercury is contained in the negative
electrode zinc in general, it is needless to say that the present
invention is effective also when the purity of the zinc is high or when
the content of mercury is lower than that.
Thus, the present invention is very effective in manufacturing the button
type alkaline cell containing a very little amount of mercury or no
mercury at all in particular and having a good self-discharge
characteristic by combining the negative electrode can made from steel
provided with Cu as a raw material and fabricated by using the die whose
part abutting at least with the Cu surface is ceramics or is coated with
ceramics, with other components of the cell, such as the positive
electrode compound, negative electrode compound, the separator, positive
electrode can, gasket, alkaline electrolyte and others.
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